I read those books dozens of times when I was a kid. But I didn't read anything into them, even though I was dragged to church 70+ times a year and actually paid attention while I was there. The phrase from the book that sticks in my mind is "always winter but never Christmas". There's no doubt the symbolism was intentional.
I'm pulling this one out of my ass, and my memory is probably faulty, but I recall a sermon one week where the Rev. referred to a CS Lewis story on the nature of hell. A group of people who lived in a cold, dark, dreary, polluted city (Manchester is the prototype, but Toledo is a great stand-in) got to go on a bus trip out to the country where it was warm and sunny and wonderful. They played and had a picnic and thoroughly enjoyed themselves, but then got back on the bus and went back to their same terrible city. The point was hell (the city) and heaven (the country) are places on earth, or states of mind. We accept living in hell like we have no other choice; we are wage slaves because we worship money and possessions, we are mean and impersonal, we ignore the commandments to love God and each other. We DO have the choice to live a heavenly life, but we are so tied into one way of thinking that we can't escape it. If this is an accurate representation of the story and its meaning, then "always winter and never Christmas" means we live in a world of death without celebrating life and love. In any case, that's the meaning I take from it.